Secondary fuel control for twostage carburetor



June 9, 1959 2,890,031

SECONDARY FUEL CONTROL FOR TWO-STAGE CARBURETOR Filed Feb. 20, 1956' H.A. CARLSON ET AL 2 Sheets-Sheet l INVENTORS HAROLD A. CARLSON ALBERT W.ZUB OLIN J. EICKMANN aa W ATTORNEY June 9, 1959 H. A. CARLSON ETAL2,890,03

SECONDARY FUEL CONTROL FOR TWO-STAGE CARBURETOR Filed Feb. 20. 1956 2Sheets-Sheet 2 FIG.5.

FIG.6.

INVENTORS HAROLD A.CARLSON ALBERT W. ZUB

OLIN J. EICKMANN ATTORNE United States Patent SECONDARY FUEL CONTROL FORTWO- STAGE CARBURETOR Application February 20, 1956, Serial No. 566,6099 Claims. (Cl. 261-23) This invention relates to a fuel system for acarburetor, and, more specifically, to a fuel system having a pluralityof fuel nozzles which operate progressively as the throttle is opened.

The invention is shown applied to the secondary stages of a multi-stage,multi-barrel carburetor of the fourbarrel type in conjunction with whichit is deemed especially useful and beneficial, for reasons appearinghereinafter.

The advantages of multi-barrel, multi-stage carburetors such as theusual four-barrel type are generally stated in many patents, such asKishline 2,193,533, Braun 2,434,- 192, Ericson et a1. 2,269,930, andothers. A reference to these particular patents will fully acquaintthose skilled in the art with sufiicient background to understand thepresent invention.

One of the reasons for the adoption of the fourbarrel carburetor was toobtain higher engine torque output over a larger range of engine speedsthan was possible with the single or dual carburetor. From the operatorspoint of view, however, any lack of smoothness in the transition fromsingle to multiple-stage operation in the four-barrel carburetor isobjectionable, which means that multi-stage performance of thefour-barrel carburetor in this respect must be comparable with that ofthe single or dual. Many dilferent expedients in car buretor structurehave been proposed and tested as solutions for this problem. Some haveconsiderable merit.

The present invention is aimed at the solution of this problem byattacking the basic fault, which has been found to be a lag in theoperation of the fuel system in the secondary stages in response toopening movement of the secondary throttle.

According to this invention, the secondary stages of the carburetor arecontrolled by two pairs of throttles one of which is mechanicallyactuated from the primary throttle, and the other of which isautomatically responsive to suction and velocity in the air flow throughthe secondary stages. Combined with these two pairs of throttles in thesecondary mixture stages is a fuel system including low, intermediate,and high speed nozzles. The operation of the low speed nozzles iscontrolled by the mechanically actuated throttles. The operation of theintermediate and high speed nozzles is controlled by the automaticallyoperated throttles.

The invention includes other novel features, one of which is an integralunit containing the fuel nozzles and velocity throttle, which isseparately constructed and adapted for assembly in the carburetor as aunit. This feature adds versatility to the construction, permitting aready means of interchangeability for required changes in flow capacityto meet different conditions of different engines.

, Further objects and advantages of the invention will become apparentas this description proceeds, when taken with. the showing in theaccompanying drawings, in which:

Fig. l is a side elevation, partly in section, of a conventionalfour-barrel carburetor showing the construction of the primary andsecondary stages and illustrating an embodiment of the invention.

Figs. 2 and 3 illustrate the mechanism for mechanical operation of thesecondary throttles from the primary throttles.

Fig. 4 is a top view of the removable nozzle unit.

Fig. 5 is a side elevation, in section, of a carburetor partly brokenaway to illustrate a modified formof the invention disclosed in Fig. 1.

Fig. 6 is a side elevation of a carburetor, partly in section, brokenaway to illustrate a still further modification of the inventiondisclosed in Fig. 1.

Fig. 1 illustrates a part of a four-barrel carburetor.

The section is taken through the primary and secondary barrels of oneside thereof. Since the carburetor as a whole forms no part of thepresent invention, it will not be described except to state that theinvention can be applied to any carburetor, and especially to anyfourbarrel type of carburetor of the multi-stage type such as shown ingreater detail by the patent to Carlson et a1. 2,715,522 of August 16,1955.

The carburetor shown in Fig. 1 has a throttle body 1, a float bowlsection 2, and an air horn 3 secured in superimposed relation, as isconventional in the art. These parts are so constructed as to provide apair of primary mixture conduits 5, one of which is shown, and a pair ofsecondary mixture conduits 6, one of which is shown. The primary mixtureconduits within the throttle valve body 1 mount a rotatable primarythrottle shaft 8 to which is secured primary throttles 9. Within theprimary mixture conduits 5 in the float bowl section 2 are primary andsecondary venturis 10 and 11. Fuel nozzles 12 project within the primaryventuri 10, and are supplied with fuel by way of main mixture passages13, cross fuel passage 14, and metering jets 15 controlled by stepmetering rods 16. The jets 15 are located within the fuel bowl 17, whichsupplies both primary fuel nozzles 12. Mixture conduits 5 also mount achoke valve 20 on a choke shaft 21. The fuel system also includes'idletubes 22 supplying fuel by way of passages 23 to the idle ports 24adjacent throttles 9. The fuel system may also be equipped with theusual air bleeds 26 and 27.

The structure so far described is conventional carburetor structure, anda further detailed description of its construction and operation willserve no useful purpose here.

Referring to Figs. 2 and 3, one end of the throttle shaft 8 carries afixed lever 30 which rotates with the shaft 8. 0n the lever 30 is a cam31 and arm 32, and a laterally extending lug 33. Rotatably mounted onthe shaft 8 is an operating lever 35 carrying a forwardly extending lug36 and an abrupt shoulder 37. A link 38 connects lever 35 with a similarlever 40 fixed to the secondary throttle shaft 41. A cam surface 42formed on the lever 40 cooperates with the cam surface 31 on the lever30. v

The portion of the mixture conduits 6 within the throttle body 1 hasthrottles 45 secured to and operated by secondary throttle shaft 41. Thesecondary throttles 45, in turn, control like idle ports 46 suppliedwith fuel from fuel bowl 47 by way of metering jets 48 and suitablepassages similar to the passages 23 on the primary side. Main fuelsupply passages 49 extend upwardly to ports formed in a shoulder 50extending com-i pletely around the periphery of both secondary mixtureconduits 6. Seated on the shoulder 50 is a block 51 in which is formed apair of venturi nozzles 52 and 53 (see Fig. 4). Each venturi has a fuelnozzle bar. 54 and 55 which are identical in construction, so that thedescription of one will serve for both.

Returning to Fig. 1, fuel bar 54 has a fuel nozzle 56 connected bysuitable passages 57 and 53 with a port in the bottom of the block 51registering with the passage 49. In the fuel passage 57 is a meteringrestriction 59 for controlling the connection with a well 66 containingvent tube 61. The well 6% is supplied with fuel from the main fuelpassage 49.

Returning to Fig.- 4, the block 51 is transversely bored for supportinga throttle shaft 65 eccentrically mounted with respect to the venturi 52and 53 and the secondary mixture conduits 6. This shaft supports a pairof unbalanced throttle plates 66 and 67 so mounted that one edge of eachcontrols a fuel port 70 connecting with the passages 58.

Within the block 51 is a recess or slot 72 which receives a weight 73secured on an arm 74 and, in turn, rigidly fixed to the throttle shaft65. The weight 73 tends to retain the throttles 66 and 67 closed againstthe force of suction acting upon the unbalanced throttles.

The block 51 containing the venturi 52 and 53 is secured in place withinthe float bowl section 2 by the float bowl cover on the air horn 3. Itis thus readily removable and replaceable, and may be manufactured invarying sizes to fit any carburetor, so that in each carburetor the sizeof the secondary fuel passages is readily variable by means of theinterchangeability provided.

Operation As shown in Fig. 2, opening movement of the primary throttles8, which are usually manually controlled, moves the lug 33 into contactwith the shoulder 37 at the same time cam surface 31 is moved withrespect to cam surface 42. Further opening movement of the primarythrottle from the position shown in Fig. 2 is transmitted to thesecondary throttle shaft 41 through the link 38. This connection is soconstructed that both throttles, primary and secondary, will reach awide-open position simultaneously.

During the reverse action, the closing movement of the primary throttleshaft engages the cam surfaces 31 and 42 to move the secondary throttleshaft 41 in a direction to close the secondary throttles 45. Duringclosing movement, lug 36 is engaged by arm 32. so as to positiv'elyclose the secondary throttles.

' When the engine is operating with both throttles closed, fuel will befed to the engine by way of idle ports 24 in the primary mixtureconduits secondary mixture conduits 6. With both the primary andsecondary throttles open, the degree of suction present will determinethe position of the velocity throttles 66 and 67, which will beyieldingly urged to the closed position by the Weight 73 on the arm 74.However, when the velocity throttles 66 and 67 begin to open, theyimmediately uncover a portion of the fuel ports 70, so that even thoughthe secondary throttles 45 have passed beyond the idle ports '46, andthese ports are no longer functioning stronger for this reason, fuelwill be immediately available from the fuel port 76 at the edge of thethrottles 66 and 67 due to the presence of suction below thesethrottles, since engine suction is necessary to open these throttles forthe passage of air. The fuel ports 70 will continue to function stronglyuntil after the unbalanced throttles. 66 and 67 have reached a positionfar enough to effect a fuel flow directly from the main fuel nozzles 56.

The embodiment illustrated in Fig. 5 differs from that shown in Figs. 1and 4 only to the extent that the fuel nozzles '56 and 70 areinterconnected with the main fuel supply passages '49 by separatepassages, one indicated as 58 and the other as 58. Otherwise theconstruction is identical, and a further description is deemedunnecessary for a complete understanding of the particular construction.I

Operation operation of the other.

5 and idle ports 46 in the I sumption, second discharge means In themodification shown in Fig. 6, the construction is identical with thatabove described except that the main fuel nozzles 56 open directly intothe throat of the venturi 52 and 53. Otherwise the modification has thefuel ports 70 and similar passages 58 and 57 connecting with main fuelpassages 49 and with wells 60, all as above described.

Operation The operation of Fig. 6 is similar to that already describedabove, and can be clearly understood from the preceding detaileddescription.

A construction has been described which will fulfill all the objects ofthe invention set forth above, but it is contemplated that still othermodifications will occur to those skilled in the art which come withinthe scope of the appended claims.

We claim:

1. In a multi-stage, multi-barrel carburetor, the combinationcomprising, primary and secondary mixture conduits, manually controlledthrottle valves in said primary and secondary mixture conduits, aventuri nozzle in said secondary mixture conduit anterior of saidthrottle valve, a suction operated valve controlling the flow throughsaid venturi, and a fuel supply system for said secondary mixtureconduit including, a source of fuel, an idle port supplied from saidsource and located adjacent the edge of said manually operated throttle,a high-speed fuel nozzle connected to said source and discharging insaid venturi, and a low-speed nozzle supplied from said source andlocated at the upper edge of said suction operated valve so as to beexposed to the effect of differential pressures acting to open saidsuction operated valve.

2. The combination defined in claim 1, including a nozzle bar extendingtransversely of said venturi in which said high-speed nozzle is located.

3. The combination defined in claim 1 in which said low-speed nozzle issupplied from said source through said connection between the high-speednozzle and said source.

4. In fuel systems for engines, the combination comprising, valve meansopening responsive to increases in air requirements of said engine,first discharge means for delivering fuel through a range of relativelylow fuel confor delivering fuel through a range of relatively high fuelconsumption when said valve means is open a given minimum amount, saidfirst discharge means functioning independently of said valve means, andthird discharge means responsive to opening of said valve means lessthan said given amount to provide an intermediate amount of fuel untilsaid valve means has opened said given amount and said second dischargemeans is brought into operation.

5. In fuel systems for engines, the combination comprising, air valvemeans opening responsive to increases in air requirements of saidengine, first discharge means for delivering fuel through a first rangeof relatively low fuel consumption, second discharge means fordelivering fuel through a second range of relatively high fuelconsumption when said air valve is open a given minimum amount, saidfirst discharge means functioning independently of said air valve, andthird discharge means responsive to opening of said air valve less thansaid given amount and to suction downstream of said air valve to providean intermediate amount of fuel until said air valve has opened saidgiven amount and said second discharge means is brought into operation.

6. A fuel supply system for an internal combustion engine comprising, anair duct, a main throttle valve in said duct, main and idling fuelsupply passages discharging into said duct through ports locatedrespectively upstream and downstream of said valve when in its idlingposition, an auxiliary throttle valve between said main fuel dischargeport and said main throttle valve, an auxiliary fuel supply port in aportion of the Wall of said duct traversed by the edge of said auxiliaryvalve and connected to said main fuel passage, and means responsive tovariation of speed of the associated engine for actuating said auxiliaryvalve, said auxiliary supply port being positioned relative to saidauxiliary valve so as to be exposed to engine suction downstream of saidauxiliary valve during initial opening of said auxiliary valve to causethe feeding of fuel through said auxiliary port before said main fuelport starts to feed.

7. In a carburetor, a fuel chamber, an induction conduit, a main fueldischarge nozzle in said induction conduit discharging fuel responsiveto a given minimum flow of air through said induction conduit, avelocity valve in said induction conduit, a manually controlled throttlevalve in said induction conduit downstream from said nozzle and saidvelocity valve, idle fuel discharge means for discharging fuel when saidthrottle valve is substantially closed, an intermediate fuel dischargeport in said induction conduit adjacent to and upstream from saidvelocity valve when closed, a fuel supply passage between said fuelchamber and said main discharge nozzle, and a fuel supply connectionbetween said intermediate port and said passage.

8. In a multi-stage, multi-barrel carburetor, the combination comprisingprimary and secondary mixture conduits, manually controlled throttlevalves in said primary and secondary mixture conduits, a venturi in eachsaid primary and secondary mixture conduits anterior to said throttlevalves, a suction operated valve controlling the flow through theventuri in said secondary mixture conduit, and a fuel supply system forsaid carburetor including a source of fuel, idle ports in said mixtureconduits supplied from said source and located adjacent the edge of eachof said manually operated throttle valves, high speed fuel nozzlesconnected to said fuel source and discharging into said venturis, and alow speed nozzle supplied from said source and located at the edge ofsaid suction operated valve in said secondary mixture conduit so as tobe exposed to the effect of differential pressure acting to open saidsuction operated valve.

9. In a multi-stage, multi-barrel carburetor, the combination comprisingprimary and secondary mixture conduits, manually controlled throttlevalves in said primary and secondary mixture conduits, a venturi in eachsaid primary and secondary mixture conduits anterior to said throttlevalves, a suction operated valve controlling the flow through theventuri in said secondary mixture conduit, and a fuel supply system forsaid carburetor including a source of fuel, idle ports in said mixtureconduits supplied from said source and located adjacent the edge of eachof said manually operated throttle valves, high speed fuel nozzlesconnected to said fuel source and discharging into said venturis, and alow speed nozzle located between the idle ports and the high speed fuelnozzles, said low speed nozzles being supplied with fluid from saidsource and located adjacent the edge of the suction operated valve insaid secondary mixture conduit.

References Cited in the file of this patent UNITED STATES PATENTS1,618,244 Udale Feb. 22, 1927 1,904,634 Teeter Apr. 18, 1933 1,929,266Viel Oct. 3, 1933 2,162,056 Bracke June 13, 1939 2,271,114 Bracke Jan.27, 1942 2,703,229 Henning Mar. 1, 1955

